Electronic apparatus and cooling module mounted in that electronic apparatus

ABSTRACT

An electronic apparatus includes a fan, a circuit board which is positioned downstream in an airflow to which the fan generates, at least one processer mounted on the circuit board, a radiator which is positioned downstream in the airflow which the fan generates, the radiator cooling a liquid coolant, a pipe unit which includes a heat receiving member in which the coolant flows and coolant piping, the heat receiving member being mounted on the processer, and the coolant piping circulating the liquid coolant between the radiator and the heat receiving member, and at least one memory board on which memory package is mounted, the memory board being mounted on the circuit board, and the memory board and the pipe unit being arranged along a direction perpendicular to a direction to which the fan blows the airflow.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 13/673,282, filed on Nov. 9, 2012, which claims priority from, andincorporates by reference the entire disclosure of, Japanese PatentApplication No. 2012-197918, filed on Sep. 7, 2012.

FIELD

The present application relates to an electronic apparatus which is ableto cool high heat generating components, which are arranged aligned,with a high efficiency and to a cooling module which is mounted in thatelectronic apparatus.

BACKGROUND

In recent years, servers and other electronic apparatuses have been madehigher in speed and more advanced in functions. Such electronicapparatuses mount large numbers of electronic devices. These electronicdevices generate heat along with their operation. One of theseelectronic devices, the CPU (central processing unit), is now consumingincreased power due to its higher speed and more advanced functions. Theamount of heat generated by a CPU tends to increase the greater thesupplied power. Further, in general, a server mounts a plurality ofCPUs. The amount of heat which is generated from these becomestremendous. If the heat causes the inside of the server to become highin temperature, the functions of the electronic devices will becomeimpaired and malfunction of the server will be caused. Therefore, tomaintain the functions of the electronic devices and avoid malfunctionof the server, the heat generating electronic devices need to be cooled.

As a radiator which takes heat from heat generating electronic devicesand discharges it to the outside, there is known a liquid cooling systemwhich runs coolant through coolant piping and uses its passage so as totake heat from the electronic devices and discharges the heat to theoutside (for example, Japanese Laid-Open Patent Publication No. 5-109798and Japanese Laid-Open Patent Publication No. 2005-381126). A liquidcooling system in general is provided with heat receiving units, aradiator, pumps, a manifold, and a plurality of pipes which connectthese with each other to form a closed path. The heat receiving unittakes heat from the CPUs using the coolant, while the radiatordischarges the heat of the coolant which has become high in temperaturedue to the taken heat to the air or other outside part. The coolantwhich flows through the channels which are formed by the piping issupplied with the force for running through the channels by the pumps.The manifold divides and merges the coolant which flows through thechannels.

In this regard, since a liquid cooling system has such a plurality ofcomponents, when applying the liquid cooling system to a server, sincethere is a limit to the space inside of the server, the layout of thecomponents inside the server has to be considered or else mounting isnot possible. Further, in a server, an air cooling system which usesfans is mounted for cooling the electronic components other than theCPUs. The fans are used to take in outside air as the cooling air so asto cool the electronic components and to discharge to the outside thecooling air which has become high in temperature due to the taken heat.For this reason, if mounting a liquid cooling system in addition to theexisting air cooling system, there is the problem that the flow of thecooling air which is supplied by the air cooling system will be blockedby the components of the liquid cooling system and cooling will beobstructed. Mounting has therefore been difficult.

Furthermore, a server or other electronic apparatus is installed in adata center or computer room or other cramped location, so the placeswhere it can be installed are limited. To enable a large number ofservers to be installed in such limited locations, reduction of theserver size and reduction of the area occupied at the time ofinstallation are sought. In this regard, in recent years, servers havebeen expanded in functions and performance, so the work, calculations,etc. which used to be performed by a large number of servers can now beperformed by a smaller number of servers. Also, individual servers havealso been improved in performance, so the area which the hardwareoccupies has been reduced. This improvement of the functions which theservers can perform and improvement of the performance of the servershave led to higher density mounting of electronic components in theservers. When mounting electronic components in servers at such a higherdensity, the issue arises of how to efficiently cool the heat generatingelectronic components.

SUMMARY

The present application provides an electronic apparatus includes a fan,a circuit board which is positioned downstream in an airflow to whichthe fan generates, at least one processer mounted on the circuit board,a radiator which is positioned downstream in the airflow which the fangenerates, the radiator cooling a liquid coolant, a pipe unit whichincludes a heat receiving member in which the coolant flows and coolantpiping, the heat receiving member being mounted on the processer, andthe coolant piping circulating the liquid coolant between the radiatorand the heat receiving member, and at least one memory board on whichmemory package is mounted, the memory board being mounted on the circuitboard, and the memory board and the pipe unit being arranged along adirection perpendicular to a direction to which the fan blows theairflow.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective view which illustrates the appearance of aserver which mounts a plurality of server modules which are providedwith cooling modules according to the present application.

FIG. 1B is a partially enlarged view which illustrates a state ofpulling out one server module from a rack cabinet of the server which isillustrated in FIG. 1A.

FIG. 1C is a perspective view which illustrates a general internalconfiguration of one server module which mounts an air cooling system.

FIG. 2A is an assembled view which illustrates a state of mounting aliquid cooling module according to the present application in a servermodule of a first embodiment of the present application which isprovided with an air cooling system.

FIG. 2B is a plan view which illustrates a state of a cooling modulemounted in a server module which is provided with an air cooling systemwhich is illustrated in FIG. 2A.

FIG. 3A is an assembled perspective view which illustrates a state ofmounting the cooling module according to the present application at amain board in a server module which is provided with the cooling modulewhich is illustrated in FIG. 2A.

FIG. 3B is a perspective view of the server module which is illustratedin FIG. 2B.

FIG. 4 is an enlarged perspective view of principal parts whichillustrates a tank and pumps in the cooling module which is illustratedin FIG. 3A.

FIG. 5A is a vertical cross-sectional view which illustrates one exampleof the internal structure of the tank which is illustrated in FIG. 4.

FIG. 5B is a cross-sectional view along the line B-B of FIG. 5A.

FIG. 6A is a perspective view which illustrates one embodiment of thestructure of a connecting part of fins and coolant piping of a radiatorwhich is illustrated in FIG. 3.

FIG. 6B is a front view of the radiator which is illustrated in FIG. 6A.

FIG. 7A is an explanatory view which explains a flow of coolant in thecooling module which is illustrated in FIG. 2A and FIG. 3A.

FIG. 7B is a circuit diagram which illustrates one embodiment of theconfiguration of a control circuit of pumps in the cooling module whichis illustrated in FIG. 7A.

FIG. 8 is a flow chart which illustrates an embodiment of a controlroutine of the pumps which is illustrated in FIG. 7B.

FIG. 9 is an explanatory view which illustrates the layout of heatgenerating components and memories in a server module according to thepresent application and the layout of a cooling module which cools theheat generating components.

FIG. 10 is a disassembled perspective view which illustrates specificcomponent members of a cooling module according to the presentapplication.

FIG. 11A is a comparative view which compares the flow of the coolingair which flows through the inside of a server module which is providedwith an air cooling system and the flow of the cooling air in the caseof providing a wall at a center part inside of the server module.

FIG. 11B is a cross-sectional view which illustrates an embodiment wherethe wall is covered by a ceiling part.

FIG. 11C is an explanatory view which illustrates the flow of thecooling air in the case of providing a curved part at an upstream sideof the wall.

FIG. 11D is an explanatory view which illustrates the flow of thecooling air in the case of providing a tapered part at an upstream sideof the wall.

FIG. 12 is an assembled perspective view which illustrates an embodimentwhich arranges a leakage tray between a cooling module and a main boardwhich are illustrated in FIG. 3A.

FIG. 13A is a perspective view which illustrates the state of mounting aleakage tray and a water cooling system on the main board which isillustrated in FIG. 12.

FIG. 13B is a cross-sectional view of principal parts of the servermodule which is illustrated in FIG. 13A.

FIG. 14A is a cross-sectional view of principal parts of the servermodule which is illustrated in FIG. 13.

FIG. 14B is a schematic cross-sectional view which illustrates thestructure of the leakage tray which illustrates a second embodiment ofthe leakage tray which is illustrated in FIG. 14A.

FIG. 14C is a schematic cross-sectional view which illustrates thestructure of the leakage tray which illustrates a third embodiment ofthe leakage tray which is illustrated in FIG. 14A.

FIG. 14D is a schematic cross-sectional view which illustrates thestructure of the leakage tray which illustrates a fourth embodiment ofthe leaking water prevention structure of the cooling module which isillustrated in FIG. 14A.

FIG. 15A is a partially enlarged perspective view which illustrates theconfiguration of six pumps and heat receiving members which are arrangedat the two sides of the tank of the cooling module.

FIG. 15B is a partially enlarged perspective view which illustrates aholding structure which holds at a slant the six pumps which areillustrated in FIG. 15A.

FIG. 16 is a plan view which illustrates a second embodiment of a servermodule 1 which mounts an air cooling system and the cooling module ofthe present application.

FIG. 17 is a plan view which illustrates the state of cooling air of theair cooling system being supplied to a connection mechanism of top andbottom server modules which are provided at the rear surface side of theserver module of the second embodiment which is illustrated in FIG. 16.

FIG. 18 is an assembled perspective view which illustrates a thirdembodiment of the present application where a single server modulemounts two main boards on which cooling modules are mounted.

FIG. 19 is a perspective view which illustrates the structure of abottom surface of a top side main board which is illustrated in FIG. 18.

FIG. 20 is a perspective view of principal parts of the server module inthe state where a first system unit which is illustrated in FIG. 18 hasa second system unit laid over it.

DESCRIPTION OF EMBODIMENTS

Below, the attached drawings will be used to explain modes of workingthe present application in detail based on specific embodiments. Notethat in the embodiments which are explained below, as the electronicapparatus, a server module which forms a server is explained as anexample, but the electronic apparatus is not limited to this. Further,in the following embodiments, component members which are provided withthe same functions will be assigned the same reference numerals for theexplanations.

FIG. 1A is a perspective view which illustrates the appearance of a rackmount server 100 in which a server module 1 which is provided with aliquid cooling system according to the present application is mounted ina rack cabinet 9. The rack mount server 100 is one type of dataprocessing system. Inside the rack cabinet 9, one or more server modules1 are mounted. The cooling air for cooling the server module 1 is suckedin from the front surface, cools the internal devices of the servermodule 1, and is exhausted from the rear surface.

FIG. 1B is a partially enlarged view which illustrates the state whenpulling out one server module 1 from the rack cabinet 9 which isillustrated in FIG. 1A. Further, FIG. 1C is a perspective view whichillustrates the configuration of the air cooling system which is mountedin one server module 1. Inside the server module 1, the first heatgenerating components 2 are at the upstream side of the fans 5 withrespect to the flow of the cooling air, while at the downstream side ofthe fans 5, CPUs (second heat generating components) 3, electroniccomponents 4, etc. are arranged. The first heat generating components 2are, for example, hard disks or SSDs (solid state devices) or otherelectronic components. The cooling air from the fans 5 is used to coolthe CPUs 3 and electronic components 4 and other heat generatingcomponents and electronic components.

FIG. 2A illustrates the server module 1 of one embodiment of the presentapplication and is an assembled view which illustrates by a plan viewthe state of the server module 1 which is provided with an air coolingsystem and mounts the liquid cooling system 10. Note that, after this,the liquid cooling system 10 will sometimes also be referred to as the“cooling module 10”. Further, FIG. 2B is a plan view which illustratesthe state of the server module 1 which is provided with an air coolingsystem which is illustrated in FIG. 2A and mounts the liquid coolingsystem 10. The air cooling system is provided with a plurality of fans 5which generate cooling air. The main board 6 at the upstream side of thefans 5 is provided with the first heat generating components (hard disk,SSD, etc.) which were explained in FIG. 1C, but here their illustrationis omitted.

In the present application, the region on the main board 6 at thedownstream side from the fans 5 of the server module 1 is divided bylines which run in the direction of flow of the cooling air CA into afirst region A1 and second regions A2. The first region A1 is a regionin which a plurality of heat generating components (here, the heatgenerating components 3A and 3B) are arranged. The plurality of heatgenerating components 3A and 3B are arranged aligned along the directionof flow of the cooling air CA. The heat generating components 3A and 3Bare, for example, the CPUs 3A and 3B. These are large heat generatingcomponents which require strong cooling. In this embodiment, the CPU 3Bis arranged at the downstream side of the CPU 3A. Accordingly, the heatgenerating components 3A and 3B are subsequently also referred to as the“CPUs 3A and 3B” or “the components which require strong cooling 3A and3B”. The second regions A2 are regions which are positioned at the twosides of the first region A1 (sometimes at one side of the first regionA1) and contain electronic components which can be cooled by coolingair.

The CPUs 3A and 3B which are arranged at the first region A1 may not becooled sufficiently by cooling air, that is, are components whichrequire strong cooling, so are cooled by the liquid cooling system 10.The part at which the liquid cooling system 10 is arranged also hascomponents which do not require cooling air, that is, have 1 W or lessheat generating characteristics. If the CPUs 3A and 3B are arranged inthe region at which the liquid cooling system 10 is arranged, thedirection of flow of the cooling air need not be straight. Theelectronic components 4 which are arranged at the second regions A2 areelectronic components 4 which can be cooled by the supply of cooling airor which can be cooled by the supply of cooling air and the attachmentof a heat sink or other radiator and which have 1 W to 100 W or so heatgenerating characteristics. They are also called “components whichrequire weak cooling”. As such electronic components 4, there are DIMMs(memory modules), power components, etc.

The above-mentioned first region A1 and second regions A2 are elongatedrectangular regions. Non-tapering regions are secured. This is becauseif the regions on the main board 6 are finely divided by the componentsetc. of the liquid cooling system 10, the distance between air cooledcomponents will be limited by the liquid cooling system 10 andrealization of the circuit configuration which the system requires willbecome difficult. The position of the first region A1 on the main board6 is determined by the sizes and positions of the second regions A2, butin general is a position slightly offset from the center part of themain board 6. Further, the second regions A2 which are positioned at thetwo sides of the first region A1 may not be the same.

In the present application, the region on the main board 6 at thedownstream side of the cooling air CA of the air cooling system isdivided into the first region A1 and the second regions A2. In thisserver module 1, a liquid cooling system 10 designed not to interferewith the cooling air CA to the second regions A2 is mounted at the firstregion A1. The liquid cooling system 10 is in general provided with aradiator which cools the coolant, heat receiving members which take heatfrom the heat generating components (absorb heat from them), coolantpiping which runs coolant from the radiator to the heat receivingmembers, and pumps which make the coolant in the coolant piping move.The heat receiving members are also called “cooling jackets”.

In the embodiment which is illustrated in FIGS. 2A and 2B, the radiator11 is provided at the downstream side of the fans 5 so that it issufficiently cooled by the cooling air CA. Usually, it is provided inthe direction vertical to the direction of flow of the cooling air CA.It is arranged so that all of the cooling air CA which is supplied bythe fans 5 can be supplied to it. The length of the radiator 11 isshorter than the total length of the plurality of aligned fans 5. Theheat receiving members 12 are provided on the CPUs 3. The coolant piping13 which supplies coolant to the heat receiving members 12 from theradiator 11 is provided on the main board 6 so as not to enter thesecond regions A2. The radiator 11 has a plurality of channels. Thecoolant piping 13 is connected by the manifold 16 to the plurality ofchannels of the radiator 11. Further, between the coolant piping 13 andthe heat receiving member 12, tanks 15 which temporarily store thecoolant and pumps 15 which move the coolant are provided. Theconfiguration of the pumps 14 will be explained in detail later, butpluralities are provided at the two sides of the tanks 15. Note that, ifthe pumps 14 are large in capacity, the pumps 14 may also be provided atjust single sides of the tanks 15.

Due to this structure, the heat receiving members 12 has the pumps 14and the tanks 15 arranged concentrated on them in adjoining manners, sothe coolant piping 13 which connects these can be shortened and spacecan be saved. Further, the channel resistance when the coolant flowsthrough the inside of coolant piping 13 depends on the length of thecoolant piping 13, so by making the coolant piping 13 shorter, thechannel resistance of the coolant which flows through the inside of theliquid cooling system 10 can be made smaller. Further, by the amount ofmovement of the coolant becoming greater, heat is efficientlytransferred from the heat receiving units 12 to the radiator 11, so theliquid cooling system 10 can be improved in performance.

Furthermore, the components which require strong cooling areconcentrated at the first region A1 while avoiding the second regions,so the components of the liquid cooling system 10 can also beconcentrated at the first region A1. As a result, the second regions A2can be secured wide without being made narrow. On top of this, theliquid cooling system 10 does not inhibit the flow of cooling air CA tothe second regions A2 and can sufficiently supply cooling air CA to theelectronic components 4 which are mounted at the second regions A2. Dueto these advantages, the performance of the liquid cooling system 10 isimproved and it becomes possible to mount at the server a liquid coolingsystem 10 which cools heat generating components 3A and 3B which have300 W or so high heat generating characteristics while not interferingwith the cooling of electronic components 4 which use cooling air CA forcooling.

FIG. 3A is an assembled perspective view which illustrates the state ofmounting the liquid cooling system 10 on the main board 6 which isillustrated in FIG. 2A, while FIG. 3B is a perspective view of theserver module 1 which is illustrated in FIG. 2B. As will be understoodfrom these figures, the electronic components 4 include a large numberof electronic components which are mounted on one or both surfaces of asub board 4A. The sub board 4A is attached to a socket 4B which isprovided on the main board 6. Further, a single tank 15 has six pumps 14connected to it in parallel, so the flow rate of the coolant can beincreased.

Here, FIG. 9 will be used to explain the features of the layout of subboards 4A on which the electronic components 4 are mounted and theconnection with the CPUs 3A and 3B. Here, the electronic components 4are memories (DIMM). The DIMMs 4 are structured as sub boards 4A on bothor one side of which a plurality of DRAM devices are mounted. Below, theelectronic components 4 will also be referred to as “memories 4” or“DIMMs 4”. Pluralities of the sub boards 4A are arranged in parallelwith the flow of the cooling air CA at the two sides of the CPUs 3A and3B. For this reason, the physical wiring lengths between the DIMMs 4 andthe CPUs 3A and 3B can be made the shortest.

Inside of the CPUs 3A and 3B, there are system controllers 3S and memoryaccess controllers 3M. The memories 4 transfer data with the CPUs 3A and3B through the memory access controllers 3M and the system controllers3S. Data transfer between devices takes time corresponding to the lengthof wiring between the devices (physical distance). During that time, thedata processing at the CPUs is stopped. In the present embodiment, asexplained above, the physical length of wiring between the memories 4and the CPUs 3A and 3B can be made the shortest, so the time untilcompletion of transfer of data (memory latency) is small and the timerequired for data processing in the system as a whole can be shortened.

That is, in the present embodiment, the layout of the CPUs 3A and 3B andthe memories 4 is given the greatest priority to in the design of themain board 6. The liquid cooling system 10 is arranged in accordancewith the layout of the components which require strong cooling 3 on themain board 6. For this reason, in the present embodiment, the liquidcooling system 10 is arranged at a location offset from the center ofthe main board 6, while the air cooling system has a left-rightasymmetric area ratio.

FIG. 4 is an enlarged perspective view which illustrates the principalparts of structures of the coolant piping 13, pumps 14, and a tank 15 inthe liquid cooling system 10 which is illustrated in FIG. 3A. Thecoolant piping 13 is provided with a cold water pipe 13C through whichlow temperature coolant which was cooled at the radiator flows and awarm water pipe (not illustrated) through which high temperature coolantwhich had absorbed the heat of the heat generating components and risenin temperature flows. The cold water pipe 13C is connected to the tank15. The tank 15 is provided with six pumps 14. The pumps 14 suck incoolant which was temporarily stored inside the tank 15 by the suctionpipes 14S and return it through the discharge pipes 14D to the inside ofthe tank 15. The six pumps 14 are attached to the tank 15 in diagonallyslanted states so as to lower the heights from the heat receivingmembers 12. The coolant which is returned from the six pumps 14 to theinside of the tank 15 merges, passes through the cold water pipe 13C,and is supplied to the not illustrated heat receiving members. Thestructure of the heat receiving members will be explained later. At theinside of the pump 14, while not illustrated, backflow of coolant at thetime of pump breakdown is prevented.

FIG. 5A is a vertical cross-sectional view which illustrates one exampleof the internal structure of a tank 15 which is illustrated in FIG. 4,while FIG. 5B is a cross-sectional view along the line B-B of FIG. 5A.As will be understood from these figures, the tank 15 is dividedinternally into two chambers by a partition wall 15W. One chamber is astorage chamber 15S to which the coolant piping 13 which is connected tothe radiator and the suction pipes 14S of the pumps 14 are connected.The other chamber is a mixing chamber 15M to which the cooling piping 13which is connected to the heat receiving members and the discharge pipes14D of the pumps 14 are connected. The storage chamber 15S receives andtemporarily stores the coolant which flows in from the radiator. At thistime, the air which is contained in the coolant builds up at the ceilingpart of the storage chamber 15S. The suction pipes 14S of the pumps 14are connected to parts close to the bottom surface of the storagechamber 15S so as to suck out coolant, so air which has built up at theceiling part of the storage chamber 15S will never enter the pumps 14.The mixing chamber 15M receives and mixes coolant from the pumps 14flowing in through the discharge pipe 14D and discharges the mixturefrom the coolant piping 13. The partition wall 15W is not limited inshape to this embodiment.

FIG. 6A is a perspective view which illustrates the configuration of oneembodiment of the radiator 11 in the present application, while FIG. 6Bis a front view of the radiator 11 which is illustrated in FIG. 6A. Theradiator 11 of this embodiment is provided with four radiating channelsat the left side and four radiating channels at the right side centeredabout a manifold 16. The channels are shaped from flat channels whichare bent back in a U-shape. Between the facing channels, corrugated fins11F are provided for raising the radiating efficiency.

The channels are connected to the manifold 16. The manifold 16 has acoolant inlet part 16H and a coolant outlet part 16C. The coolant inletpart 16H is connected inside of the manifold 16 to first end parts ofthe four radiating channels at the left side of the manifold 16, whilethe coolant outlet part 16C is connected inside of the manifold 16 tofirst end parts of the four radiating channels at the right side of themanifold 16. The other end parts of the left side and right sideradiating channels which are not connected to the coolant inlet part 16Hand the coolant outlet part 16C are connected inside of the manifold 16.

The coolant (warm water) which flows to the coolant inlet part 16H fromnot illustrated coolant piping flows into the four radiating channels atthe left side of the manifold 16, makes U-turns at the end parts,returns to the manifold 16, then flows into the four radiating channelsat the right side of the manifold 16. The coolant which flows into thefour radiating channels at the right side of the manifold 16 makesU-turns at the end parts to again return to the manifold 16, isdischarged from the coolant outlet part 16C, and flows into notillustrated coolant piping. The coolant which flows in from the coolantinlet part 16H is warm water, but the coolant which is discharged fromthe coolant outlet part 16C is cooled by the radiating channels of theradiator 11, so is cold water.

FIG. 7A is an explanatory view which explains the flow of coolant in theliquid cooling system 10 which is illustrated in FIG. 2A and FIG. 3A,while FIG. 7B is a circuit diagram which illustrates an embodiment ofthe configuration of the control circuit of the pump in the liquidcooling system 10 which is illustrated in FIG. 7A. As explained above,the coolant is cooled by the radiator 11, flows through the cold waterpipe 13H into the tank 15, and is sent by the pumps 14 to the heatreceiving member 12 to cool the heat generating components. The raisedtemperature coolant is then returned through the warm water pipe 13H tothe radiator 11.

The pumps 14, while not illustrated, have speed detection sensorsattached to them. The operations of the pumps 14 are monitored by acontrol circuit (service processor) 20 to which the speed signals (pulsesignals) are input. The control circuit 20 includes conversion circuits21 which convert pulse signals to speed signals, threshold valuejudgment circuits 22 which compare the speeds of the pumps 14 against athreshold value, and a component judgment circuit 23 and system judgmentcircuit 24 which use the outputs from the threshold value judgmentcircuits 22 to judge if the pumps 14 are normal.

For example, when, among the six pumps 14, just one pump 14 has brokendown, the speed signal from that one pump 14 is not input to the controlcircuit 20, but the control circuit 20 judges that with breakdown ofjust one pump, the cooling of the heat generating components by theliquid cooling system 10 is not hindered. Further, the componentjudgment circuit 23 outputs a notification of breakdown of one of thepumps 14, but the system judgment circuit 24 outputs a command forcontinuation of operation (OK) of the liquid cooling system so thecooling of the heat generating components by the liquid cooling system10 is continued. By giving redundancy to control of the pumps 14 in thisway, even when a pump 14 breaks down, if the cooling ability can besecured, the liquid cooling system 10 does not stop and the CPUs cancontinue to be cooled, so the reliability can be secured.

FIG. 8 is a flow chart which illustrates one embodiment of a controlroutine of the control circuit 20 of the pumps 14 which is illustratedin FIG. 7B. At step 801, the operation of the liquid cooling system isstarted. At step 802, the control circuit 20 reads the speeds x of thepumps. While the server module is operating, the speeds of the pumps areconstantly monitored by the control circuit. Further, at step 803, it isjudged if the speeds x of the pumps have reached the threshold value(2050 rpm) or more. When the speeds x of all of the pumps have reachedthe threshold value or more (YES), the routine returns to step 802 wherethe speeds x of the pumps continue to be read.

On the other hand, if the judgment at step 803 is that there is a pumpwhere the speed x has not exceeded the threshold value (NO), the routineproceeds to step 804 where breakdown of that pump is notified, then theroutine proceeds to step 805. At step 805, it is judged if just one pumphas broken down. If just one pump has broken down (YES), as explainedabove, it is judged that the cooling of the heat generating componentsby the liquid cooling system is not hindered and the routine returns tostep 802 where the speeds x of the pumps continue to be read. In thisregard, when it is judged at step 805 that several pumps have brokendown (NO), it is judged that the cooling of the heat generatingcomponents by the liquid cooling system is hindered and the routineproceeds to step 806 where the operation of the cooling system isstopped and this routine is ended.

FIG. 10 is a disassembled perspective view which illustrates in detailthe configuration of members under the pumps 15 and the tanks 15 in theliquid cooling system 10 according to the present application. Under thepumps 14 and the tanks 15, there are pump support mechanisms 50 and heatreceiving members 12. The heat receiving members 12 are fastened by heatreceiving member fastening parts 17 to the top of a not illustrated mainboard. At the inside of the heat receiving member fastening parts 17,female threads are formed. These engage with male screws 19 which areillustrated in FIG. 12. The pump support mechanisms 50 are provided withpump placers 51, base plates 52, mounts 54, and brackets (pump mountingfittings) 55. Further, each heat receiving member 12 is provided with ametal plate 40, CPU-use metal plate 60, and cold plate 90.

The metal plate 40 has a step part 41, a CPU power source-use metalplate part 42, a CPU-use metal plate part 43, a hole 44 for avoidinginterference with the mounted components, a recessed part 45, and holes46 for insertion of the heat receiving member fastening parts 17. TheCPU-use metal plate 60 has a base plate 61 and mounting holes 62 forinsertion of the heat receiving member fastening parts 17. The coldplate 90 has a cold water inlet 91, coolant channel 92, CPU-use coldplate 93, U-turn channel 94, and CPU power source-use cold plate 95. Themembers which form the metal plate 40, CPU-use metal plate 60, and thecold plate 90 will be explained in detail later using enlarged drawings.

Here, the air barrier wall and the leakage tray which are provided atthe server module of the present application will be explained. FIG. 11Ais a comparative view which compares the flow of cooling air CA whichflows through the inside of the server module 1 which is provided withthe air cooling system and the flow of cooling air CA in the case ofsetting an air barrier wall 7 at the center part of the inside of theserver module 1. When the server module 1 does not have the air barrierwall 7 inside it, the cooling air CA which is generated by the fansmainly flows over the main board 6 at which the low height heatgenerating components 3 (CPUs 3A and 3B) are mounted since the partswhere the electronic components 4 are concentrated have channelresistance.

Channel resistance is generated due to the narrow interval betweencomponents on the main board 6 due to high density mounting and the highheight of the components which are mounted at such regions. That is, theelectronic components 4 are DIMMs, power modules, and other componentswhich are formed by circuits on sub boards which are mounted verticallyon the main board 6, so are high in height. Therefore, the channels ofthe cooling air CA end up being blocked by the DIMMs, power modules,etc., so channel resistance occurs. As opposed to this, the CPUs 3A and3B are directly mounted on the main board 6, so are lower in heightcompared with DIMMs, power modules, etc. DIMMs have a height from theboard 6 of, for example, 33 mm. Further, the leakage tray 8 has a heightfrom the board 6 of, for example, 26.5 mm. The lower limit value of theheight of the leakage tray 8 for preventing leakage is about half ofthat or 13 mm, while the upper limit value of the height of the leakagetray 8 for preventing contact with the ceiling of the housing is 35 mm.If in this range of height, there will be no leakage and higherefficiency of cooling of the DIMMs and power source can be expected.

Even if the main board 6 on which low height heat generating components3 are mounted is provided which an above-mentioned such liquid coolingsystem 10 as illustrated by the broken lines, the cooling air CA flowsto around the liquid cooling system, so the cooling ability of theelectronic components 4 by the cooling air CA falls. That is, in theregion inside the broken lines, only components which require strongcooling which are covered by liquid cooling and components which requireweak cooling which have a low heat generating characteristic (includingno heat generation) of an extent not requiring air cooling are mounted.Despite the fact that the supply of cooling air is not required, thecooling air flows into this region. Therefore, the cooling air which issupplied to the electronic components 4 which relatively require thesupply of cooling air is reduced, so the cooling performance of theelectronic components 4 falls.

Therefore, to prevent the cooling air CA from flowing to around the heatgenerating components 3, the area around the liquid cooling system 10which is mounted over the heat generating components 3 is covered by anair barrier wall 7. Therefore, the cooling air CA is prevented fromflowing to the components which require strong cooling 3. As a result,the inflow of cooling air to the region which does not require thesupply of cooling air can be prevented and all of the cooling air can besupplied to the components which require weak cooling 4 where thecooling air is required, so the cooling ability of the electroniccomponents 4 by the cooling air CA is improved.

Furthermore, as illustrated in FIG. 11B, if forming a ceiling part 70above the air barrier wall 7 which is provided around the heatgenerating components 3 and the liquid cooling system 10 which aremounted on the main board 6 and covering the heat generating components3 and the liquid cooling system 10 as a whole by these, the coolingability of the electronic components 4 by the cooling air CA is improvedmuch more. Further, when providing the air barrier wall 7 around theheat generating component 3 and the liquid cooling system 10, asillustrated in FIG. 11C, if providing a curved part at the upstream sideof the air barrier wall 7 or, as illustrated in FIG. 11D, if providing atapered part at the upstream side of the air barrier wall 7, the coolingair CA more easily flows to the electronic component sides.

In this regard, in the liquid cooling system 10 which has been explainedup to here, the coolant for performing the cooling is a liquid (forexample, water), so there is a possibility of coolant leaking from thecoolant piping 13 or connecting parts of the coolant piping 13 and theheat receiving members 12, pumps 14, or tanks 15. Further, if coolantleaks from the liquid cooling system 10, the leaked coolant is liable tooverflow on to the main board 6 whereby the electronic components 4 areliable to be flooded and the circuits to short. Therefore, it isconsidered to place a leakage tray which prevents leakage of leakedcoolant to other locations below the heat receiving members, pumps 14,and tanks 15 of the liquid cooling system 10.

FIG. 12 is an assembled perspective view which illustrates the state ofinsertion of the leakage tray 8 between the main board 6 which isillustrated in FIG. 3A and the liquid cooling system 10 which is mountedon the main board 6, while FIG. 13A is a perspective view whichillustrates the state of mounting the leakage tray 8 and the liquidcooling system 10 on the main board 6. On the main board 6, assume thatthe CPUs 3A and 3B, sockets 4B for attaching sub boards, and powercircuits 30A and 30B for CPU use are mounted. Further, the liquidcooling system 10, as explained above, includes a radiator 11, heatreceiving members 12, coolant piping 13, pumps 14, tanks 15, and themanifold 16.

The leakage tray 8 is provided with a base plate 80, CPU contact-useholes 8A and 8B, power circuit contact-use holes 8HA and 8HB, and theair barrier wall 7 which sticks out from the periphery of the base plate80. The CPU contact-use holes 8A and 8B are holes for insertion of theCPUs 3A and 3B on the main board 6, while the power circuit contact-useholes 8HA and 8HB are holes for insertion of CPU-use power circuits 30Aand 30B. Further, the base plate 80 between the CPU contact-use holes 8Aand 8B is provided with a sleeve 8S. The sleeve 8S will be explainedlater.

The air barrier wall 7 is formed by extending and bending upward theouter edge part of the base plate 80 of the leakage tray 8. This isbecause the outer edge part of the base plate 80 of the leakage tray 8requires a bent part for keeping leakage from the liquid cooling system10 inside the leakage tray 8, so this bent part is extended upward toincrease the wall height and serve also as an air barrier wall 7. Ifattaching the leakage tray 8 on the main board 6 and attaching theliquid cooling system 10 over that, as illustrated in FIG. 13A, the airbarrier wall 7 sticks out around the pumps 14 and the tanks 15 andtherefore the cooling air no longer enters the region where the pumps 14and the tanks 15 are provided.

FIG. 13B is a cross-sectional view of the liquid cooling system 10 whichis illustrated in FIG. 13A in the direction vertical to the flow of thecooling air. The heat receiving member fastening parts 17 are screwcomponents with springs 17B wound around their top parts. They areinserted from the metal plate 40 side through the metal plates 40,CPU-use metal plates 60, leakage tray 8, and main board 6 and screwedinto the fastening plate 18 which is attached to the rear side of themain board 6. The springs 17B are inserted between the heads 17H of theheat receiving member fastening parts 17 and the metal plates 40 andbias the metal plates 40 to the main board 6 side. From this figure, itwill be understood that the air barrier wall 7 holds inside it all ofthe components in the range from the cold water pipe 13C and warm waterpipe 13H to the coolant channel 92 of the cold plate and that thecooling air will not enter inside the liquid cooling system 10.

On the other hand, FIG. 14A is a partial cross-sectional view of theliquid cooling system 10 which is illustrated in FIG. 13A in thedirection along the flow of the cooling air. FIG. 14A illustrates onlythe part of the CPU 3A. The cross-section of the CPU 3B side is omitted.From this figure as well, it will be understood that the heat receivingmember fastening parts 17 are screwed by the male screws 19 with thefastening plate 18 at the rear side of the main board 6 and that thesprings 17B bias the metal plate 40 from the head 17H side to the mainboard 6 side.

Here, the engaged state of the metal plate 40, CPU-use metal plate 60,and the cold plate 90 which are illustrated in FIG. 10 and the mainboard 6 and leakage tray 8 which are illustrated in FIG. 12 will beexplained using FIG. 14A. The main board 6 mounts as the CPU-use powercircuit 30A a first component 30A1 and a second component 30A2 and a CPU3A. In the state of the main board 6 having the leakage tray 8 attached,the CPU-use power circuit 30A enters the power contact-use hole 8HA ofthe leakage tray 8, while the CPU 3A enters the CPU contact-use hole 8Aof the leakage tray 8. At the surface of the base 80 of the leakage tray8 on the main board 6 side, the CPU contact-use holes 8A and 8B may besurrounded by packing. The packing is adhered around the CPUs 3A and 3Bwhereby the water-stemming effect is enhanced.

The cold plate 90 which is illustrated in FIG. 10 includes the CPU-usecold plate 93 and the CPU power source-use cold plate 95. The CPU-usecold plate 93 has two channels. The end of one channel is connected tothe cold water inlet 91, while the other end is connected to the U-turnchannel 94. The other channel has one end connected to the U-turnchannel 94, while has the other end connected to the coolant channel 92.The coolant channel 92 is divided inside it into two channels. Thecoolant channel 92 with the cold water inlet 91 and the coolant channel92 through which coolant which has passed the U-turn channel 94 returnsare not communicated. Therefore, the entire amount of the coolant whichhas passed through the U-turn channel 94 and returned to the coolantchannel 92 flows into the CPU power source-use cold plate 95 and flowsinto the warm water pipe 13H of the coolant piping 13. The flow of thecoolant is illustrated by the arrow marks in FIG. 10.

If the liquid cooling system 10 is attached over the leakage tray 8, theCPU-use cold plate 93 of the cold plate 90 which forms the heatreceiving member 12 is positioned right above the CPU 3A, while the CPUpower source-use cold plate 95 is positioned right above the CPU-usepower circuit 30A. At this time, the CPU 3A is laid over the CPU-usecold plate 93 through a heat conducting sheet 31, but the firstcomponent 30A1 of the CPU-use power circuit 30A is low in height, so isnot laid over the CPU power source-use cold plate 95. Therefore, thefirst component 30A1 of the CPU-use power circuit 30A has provided on ita metal rod 32 for contact with the CPU power source-use cold plate 95through the heat conducting sheet 31.

The CPU metal plate 60 is provided with mounting holes 62 at the fourcorners of the base plate 61. The heat receiving member fastening parts17 which are inserted through the mounting holes 62 are used to lay thebase plate 61 over the CPU-use cold plate 93.

The metal plate 40 is provided with a CPU-use metal plate part 43. ThisCPU-use metal plate part 43 is provided with holes 46 which overlap themounting holes 62 which are formed at the four corners of the base plate61. One end part of the metal plate 40 has a step part 41. This steppart 41 is provided with springiness. Further, the CPU power source-usemetal plate part 42 which follows the step part 41 is much lower thanthe CPU-use metal plate part 43 and is formed to approach the main board6 at the time of mounting. In the state where the metal plate 40 isattached by the heat receiving member fastening parts 17, the CPU-usemetal plate part 43 is laid over the base plate 61 of the CPU metalplate 60 and the CPU power source-use metal plate part 42 is laid overthe CPU power source-use cold plate 95. Further, in the state where theCPU-use metal plate part 43 of the metal plate 40 is laid over the baseplate 61 of the CPU metal plate 60, the height of the bottom surface ofthe CPU power source-use metal plate part 42 from the main board 6 islower than the height of the top surface of the CPU power source-usecold plate 95 from the main board 6. For this reason, in the state wherethe metal plate 40 is attached by the heat receiving member fasteningparts 17 and the CPU power source-use metal plate part 42 is laid overthe CPU power source-use cold plate 95, the springiness of the step part41 causes the CPU power source-use cold plate 95 to be biased by the CPUpower source-use metal plate part 42.

Due to the above such configuration, the heat which is generated by theCPUs 3A and 3B and components in the CPU-use power source component 30Awhich are arranged in the first region A1 of the main board 6 isabsorbed by the CPU-use cold plate 93 and the CPU power source-use coldplate 95.

Note that, if making the bottom plate of the leakage tray 8 forpreventing leakage from the liquid cooling system 10, as illustrated inFIG. 14B and FIG. 14C, a double layer structure, it becomes harder forthe coolant which has leaked from the liquid cooling system 10 toescape. FIG. 14B illustrates an embodiment wherein a drain 83 isprovided at a double layer bottom 84. FIG. 14C illustrates theconfiguration of an embodiment which is provided with two slanted bottomplates 85, 86. Further, it is possible to not make the leakage tray 8 adouble layer bottom but, as in another embodiment which is illustratedin FIG. 14D, insert a water absorbing sheet 87 at the bottom plate ofthe leakage tray 8 so as to make it difficult for the coolant which hasleaked from the liquid cooling system 10 to escape.

FIG. 15A is a partially enlarged perspective view which illustrates themounting state of the six pumps 14 which are arranged at the two sidesof a tank 15 of the liquid cooling system 10. As explained above, thetank 15 has six pumps 14 connected to it. The tank 15 is supplied withcoolant from the cold water pipe 13C of the coolant piping 13. Betweenthe pumps 14 and the tank 15, suction pipes 14S and discharge pipes 14Dare connected. The coolant inside the tank 15 is sucked out by the pumps14, pressurized, and returned to the tank 15. The coolant which ispressurized by the pump 14 runs from the end of the tank 15 at theopposite side to the feed side through the cold water pipe 13C and issupplied to the heat receiving members 12. The structure of the heatreceiving members 12 has already been explained, so the same componentmembers will be assigned the same reference signs and explanationsomitted. The heat absorbing coolant is returned from the CPU powersource-use cold plate 95 of the heat receiving members 12 to the warmwater pipe 13H.

FIG. 15B is a partially enlarged perspective view which removes the sixpumps 14 from the structure which was illustrated in FIG. 15A so as toexplain the structure of the pump support mechanism 50. A tank 15 isfastened to the base plate 52 of the pump support mechanism by screws 53at the mounting tabs 15A which are provided at the coolant piping 13side. Further, the base plate 52 has mounts 54 which are present at thetwo end parts of brackets 55 which are provided with three pump placers51 fastened to it by screws 53. To place the pumps 14 at a slant fromthe tank 15, the pump placers 51 are made V-grooves. At the sidesurfaces of the tank 15, discharge ports 15T for discharging coolant tothe pumps 14 and suction ports 15K for the inflow of coolant from thepumps are provided. The brackets 50 are, for example, comprised of SUS(stainless steel sheet). Further, the pump placers 51 are provided withbuffer plates between the brackets 55 and the pumps 14. These bufferplates enable any offset which occurs due to deformation of the heatreceiving members 12 and the tank 15 or dimensional tolerance at thetime of manufacture to be absorbed.

FIG. 16 is a plan view which illustrates a second embodiment of theserver module 1 in which an air cooling system and the liquid coolingsystem 10 of the present application are mounted. The server module 1 ofthe second embodiment differs from the above-mentioned embodiment in thepoint that at the rear surface side of the server module 1, a connectionunit (hereinafter referred to as an “XB unit”) 71 is provided whichconnects the main boards 6 at the server module 1 which are stacked inthe vertical direction. The XB unit 71 is provided at the second regionA2 at one side of the first region A1 which is provided with the liquidcooling system 10 and at the downstream side in the flow of the coolingair. The configuration of the liquid cooling system 10 at the firstregion A1 and the configurations of the second regions A2 which arearranged at the two sides of the first region A1 are similar to thealready explained embodiments, so the same component members will beassigned the same reference signs and their explanations will beomitted.

Like in the second embodiment of the server module 1, when the servermodule 1 is provided with the XB unit 71, at the inside of the XB unit71, as illustrated in FIG. 17, there is an XB chip 73 which generates alarge amount of heat at the time of operation. Further, this XB chip 73is a weak cooling component which requires cooling by cooling air. Forthis reason, in the second embodiment of the server module 1, the firstregion A1 and the two second regions A2 are shifted to one side withrespect to the housing of the server module 1. Cooling air CA is sentthrough the part opened by the shift to the XB unit 71.

FIG. 18 is an assembled perspective view which illustrates a thirdembodiment of the server module 1 of the present application whichprovides the server module 1 of the second embodiment which wasexplained in FIG. 16, FIG. 17 with the liquid cooling system 10 andwhich attaches two main boards 6. Here, the main board 6 which isprovided with the first and the second regions A1, A2, which mounts onthose regions the already explained heat generating components orelectronic components, and is provided with the liquid cooling system 10will be called a “system unit”. This being the case, in the servermodule 1 of the third embodiment, the first system unit U1 is firstattached on the housing, then the second system unit U2 is attached laidover the top side of the first system unit U1. The positions of theelectronic components at the main board 6 of the first system unit U1and the positions of the electronic component at the main board 6 of thesecond system unit U2 are exactly the same.

In this case, the bottom surface of the main board 6 of the secondsystem unit U2 has a connector 70 which is illustrated in FIG. 19attached to it. The connector 70 is for connecting a circuit at thesecond system unit U2 to the circuit at the first system unit U1 whenthe second system unit U2 is attached laid over the top side of firstsystem unit U2. If the first system unit U1 and the second system unitU2 are electrically connected through the connector 70, the CPUs 3A, 3Bwhich are at one main board 6 can use the data of the DIMMs 4 at theother main board 6.

The position of the connector 70 which is provided at the bottom surfaceof the second system unit U2 is the same as the position of the sleeve8S at the leakage tray 9 which is attached to the main board 6 of thefirst system unit U1. In this case, the main board 6 of the first systemunit U1 mounts a connector (pair connector) which mates with theconnector 70 which is provided at the bottom surface of the main board 6of the second system unit U2 inside the sleeve 8S of the leakage tray 8.Therefore, if the second system unit U2 is attached laid over the topside of the first system unit U1, the connector 70 which is at thesecond system unit U2 is inserted into the sleeve 8S at the first systemunit U1 and connected to the pair connector.

FIG. 20 is a perspective view of principal parts of the server module 1which illustrates the state with the first and the second system unitsU1, U2 which are illustrated in FIG. 18 stacked together. Illustrationof the fans will be omitted. As will be understood from this figure,even in the state with the second system unit U2 attached over the topside of the first system unit U1, a path for cooling air to the XB unit71 is secured. Note that, as illustrated in FIG. 18, the size of thefans 5 is a size which enables sufficient cooling air to be sent toradiators 11 which are stacked in two levels.

In this way, according to the present application, it is possible toprovide a liquid cooling system which has the ability to radiate off ahigh amount of generated heat, which can be mounted at a high density ata predetermined device while saving space, and, furthermore, whichenables a mountable area of components other than those for cooling tobe broadly secured. Further, it is possible to provide a liquid coolingsystem which has pumps for transport of coolant redundantly configuredand redundantly controlled and thereby secures a high reliability anddoes not obstruct cooling of other components besides the ones beingcooled and to provide an electronic apparatus which mounts the same.

The liquid cooling system of the present application enables cooling oftwo 300 W CPUs by a pump flow rate of 0.9 liter/min in the case of aradiator of a size of a height of 36 mm, a depth of 59 mm, and a widthof 350 mm. Further, the path of the cooling air which cools the DIMMsonly has a radiator in it, so the cooling air efficiently hits the DIMMsand therefore 256 W of DIMMs (32 8 W DIMMs) becomes possible. Further,if assuming notification of abnormalities in the pumps and replacementsbeing installed in a short time from the occurrence of theabnormalities, the possibility of two pumps simultaneously breaking downis eliminated and the possibility of system trouble occurring in theliquid cooling system can be eliminated.

Although only some exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciated that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

What is claimed is:
 1. An electronic module comprising: at least onefan; at least one main board positioned downstream in an airflow whichthe fan generates; at least one processer on the main board; at leastone memory board on the main board; and a liquid cooling unit on themain board, the liquid cooing unit including a heat receiving member inwhich a liquid coolant flows and a coolant piping, the heat receivingmember mounted on the processer, the coolant piping circulating theliquid coolant between a radiator and the heat receiving member, theradiator positioned downstream in the airflow which the fan generates,the radiator be cooling the liquid coolant, wherein the memory board andthe liquid cooling unit are parallel to a direction in which the fanblows the airflow.
 2. The electronic module according to claim 1,wherein the coolant piping is connected by a manifold to the radiator,and wherein the radiator comprises at least one radiating channel at aleft side of the manifold and at least one radiating channel at a rightside of the manifold.
 3. The electronic module according to claim 1,further comprising, at least one pump letting the liquid coolant move inthe liquid cooling unit; and at least one tank temporarily stores theliquid coolant, wherein the pump slants.
 4. The electronic moduleaccording to claim 3, wherein the pump and the tank mount on the heatreceiving member, wherein the pump slants to the heat receiving member.5. The electronic module according to claim 3, wherein the coolantpiping connects the tank, the tank connects at least one pump, the pumpsucks the liquid coolant from the tank by a suction pipe and returns theliquid coolant to the tank by a discharge pipe, the returned liquidcoolant is merged and passes through the coolant piping.
 6. Theelectronic module according to claim 5, wherein the pump and the tankmount on the heat receiving member, wherein a pair of the suction pipeand the discharge pipe connects to the tank at a slant to the heatreceiving member.
 7. The electronic module according to claim 1, whereinthe heat receiving member comprising, a first plate positioned above theprocessor; and a second plate positioned above a peripheral, wherein theliquid coolant flows in the first plate and in the second plate.
 8. Theelectronic module according to claim 7, wherein the peripheral includesat least a CPU power circuit.
 9. The electronic module according toclaim 1, further comprising, a control circuit controlling the liquidcooling unit, wherein if a revolution speed of the pump does not exceeda threshold value, the control circuit judges that the pump breaks down,if a plurality of the pump breaks down, the control circuit configuresto stop the liquid cooling unit.
 10. The electronic module according toclaim 1, wherein the pump places on a pump placer with V-groove.
 11. Theelectronic module according to claim 1, wherein the pump is attachedwith a buffer plate between the pump and a pump mounting fitting. 12.The electronic module according to claim 1, wherein a plurality of themain board are stacked vertically, the plurality of the main board areconnected with at least one connection unit including at least one chip,the airflow sent to the connection unit is sent through a third area,the third area is not a first area of the processer and a second area ofthe memory board.
 13. The electronic module according to claim 12,wherein the plurality of the main board connect with a connector. 14.The electronic module according to claim 13, wherein a memory on onemain board connects a memory on another main board electrically with theconnector.
 15. The electronic module according to claim 1, wherein theprocesser is surrounded by an air barrier wall.
 16. The electronicmodule according to claim 15, wherein a ceiling is formed above the airbarrier wall.
 17. The electronic module according to claim 15, whereinthe air barrier wall is curved or tapered.
 18. An cooling method for anelectronic module, the cooling method comprising: generating an airflowby a fan on the electronic module; cooling a memory board by theairflow; circulating a liquid coolant in a coolant piping, the liquidcoolant being between a radiator and a heat receiving member; andcooling the liquid coolant by the radiator; wherein the electronicmodule comprising; a main board positioned downstream in the airflowwhich the fan generates; a processer on the main board; the memory boardon the main board; a liquid cooling unit on the main board, the liquidcooing unit including a heat receiving member in which the liquidcoolant flows and the coolant piping, the heat receiving member mountedon the processer; the radiator positioned downstream in the airflowwhich the fan generates; and the memory board and the liquid coolingunit being parallel to a direction in which the fan blows the airflow.19. The cooling method according to claim 18, further comprising, movingthe liquid coolant in the liquid cooling unit by a pump; and storingtemporarily the liquid coolant in a tank, wherein the pump slants. 20.The cooling method according to claim 18, further comprising, suckingthe liquid coolant from a tank through a suction pipe; returning theliquid coolant to the tank through a discharge pipe; merging thereturned liquid coolant; and passing the merged liquid coolant throughthe coolant piping, wherein the coolant piping connects the tank, thetank connects a pump.
 21. The cooling method according to claim 18,further comprising, controlling the liquid cooling unit by a controlcircuit, wherein if a revolution speed of the pump does not exceed athreshold value, the control circuit judges that the pump breaks down,if a plurality of the pump breaks down, the control circuit configuresto stop the liquid cooling unit.
 22. An cooling method for an electronicmodule, the cooling method comprising: generating an airflow by a fan onthe electronic module; cooling a processer by circulating a liquidcoolant in a coolant piping being between a radiator and a heatreceiving member; cooling a memory board by the airflow over theradiator; cooling a connection unit by the airflow over the radiator anda third area, the third area not being a first area of the processer anda second area of the memory board, a plurality of the main board stackedvertically being connected with the connection unit, the airflow sent tothe connection unit being sent through the third area; and cooling theliquid coolant by the radiator; wherein the electronic modulecomprising; the main board positioned downstream in the airflow; theprocesser on the main board; the memory board on the main board; theliquid cooling unit on the main board, the liquid cooing unit includingthe heat receiving member in which the liquid coolant flows and thecoolant piping, the heat receiving member mounted on the processer; andthe radiator positioned downstream in the airflow, wherein the memoryboard and the liquid cooling unit being parallel to a direction in whichthe fan blows the airflow, wherein the plurality of main board connectwith a connector, the connector is positioned between a plurality ofprocessor, a memory on one main board connects a memory on another mainboard electrically with the connector.